The voting membership of AASHTO consists of the departments of transportation from each state in the United States, as well as that of Puerto Rico and the District of Columbia. The United States Department of Transportation, some U.S. cities, counties and toll-road operators, most Canadian provinces as well as the Hong Kong Highways Department, the Turkish Ministry of Public Works and Settlement and the Nigerian Association of Public Highway and Transportation Officials have non-voting associate memberships.

The American Association of State Highway Officials (AASHO) was founded on December 12, 1914. Its name was changed to American Association of State Highway and Transportation Officials on November 13, 1973. The name change reflects a broadened scope to cover all modes of transportation, although most of its activities are still specific to highways.

While AASHTO is not a government body, it does possess quasi-governmental powers in the sense that the organizations that supply its members customarily obey most AASHTO decisions. It is an example of a general tendency in the American style of government to outsource many governmental functions to nongovernmental organizations, whose decisions are then routinely ratified by appropriate government agencies.